US3356548A - Safety mining explosive composition of nitric acid ester of a polyhydric alcohol and yhe ternary mixture of ammonium chloride, alkali metal nitrate, and alkaline earth metal carbonate - Google Patents

Description

United States Patent SAFETY MINING EXiLdSIVE COMPOSITION OF NITRIC ACID ESTER OF A POLYHYDRIC ALCO- HOL AND THE TERNARY MIXTURE 0F AMMO- 3,356,548 Patented Dec. 5, 1967 hydric alcohols such as glycol dinitrate, glycerin trinitrate, diglycol dinitrate, etc. However, mixtures of the said nitrates can also be used. It is' preferred that the amount of gelatinous phase should be just sufficient to NIUM CHLORIDE, ALKALI METAL NITRATE, 5 render the entire explosive composition gelatinous or plas- AND ALKALINE EARTH METAL CA ONA E tic. Suitably, about 18 to 40 percent by weight of the ex- Adolf Berthmann and Paul Lingens, Leverkusen, Gerplosive composition should be gelatinous phase, preferably many, assignors to Dynamit Nobel Aktiengesellschaft, about 25 to 35 weight percent. Tmisdorf, y, a corporation of Germany According to this invention it is essential that the inp p Filed fiP 1966s 576550 organic salt component consist of a combination of am- Claims priority, application Germany, Sept. 7, 1965, monium chloride, alkali metal nitrate and alkaline earth 8 i i metal carbonate. The alkaline earth metals are exemplified by calcium, magnesium, barium or mixtures thereof. It is This invention relates to novel explosives. It more parp eferred to use calcium as the alkaline earth metal. ticularly refers to novel explosives which are gelatinous or T e alkali metals are exemplified by sodium, potassium plastic and are safer than known explosives, and lithium with preference being given to the first tWO Explosives are known which, in addition to one or more named. sensibilizing components, also contain ammonium nitrate, It has been found that the inorganic salt component ammonium hlorid or l i b t of the explosive of this invention should contain the above Upon the blasting of coal underground, gelatinou exnamed constituents in the following proportions: plosives must have a relatively high resistance to ignition Ammonium ChlOfideI alkali Hitratfi 1-211 and P by firedamp. Such explosives consist of a gelatinous phase ably 1.2-l.7: 1. (mixture of nitroglycerine d nitroglycol or diglycol i- Ammonium chloride: alkali earth carbonate: 250:1 trate thickened with nitrocellulose) and a solid phase of and Preferably inorganic salts (ammonium nitrate and inert salts, for in- 25 Alkali hitratei alkali earth Carbonate! 1-4511 and stance alkali chloride). These explosives, however, do not Preferably 315I satisfy modern safety requirements with respect to the The replacement of the known salt mixtures of igniting thereof by firedamp. In order to obtain sufficient mOIlium nitrate d i m Chl id by the ternary alt resistance to firedam i accordance ith th German mixture of ammonium chloride, alkali nitrate and alkaline Test forExplosives of Class I, a high content of inert salts a0 earth carbonate of this invention, leads surprisingly to an (about 40% NaCl) must be added. Such explosives, thereincrease in the Specific energy as W611 as to gelatinous fore, have only a low specific energy as compared with safety mining explosives which have substantially more deordinary gelatinous rock explosives. Furthermore, their flagfatiOh y- The eplacemhht 0f the known Salt IhiX- behavior in the' i-esence of heat i fa or bl tures of ammonium nitrate, ammonium chloride and cal- It is an object of this invention to provide a novel Cillm Carbonate y the ternary Salt mixture of ammonium explosive. chloride, alkali nitrate and alkaline earth carbonate of It is another object of this invention to provide an this invention, leads surprisingly to an increase in the plosive particularly useful in oal mi i solids smoke components of the explosion products, and It is a further object of this invention to provide an a lower explosion temperature and a product which meets explosive which has increased defiagration safety. the firedamp ignition standards according to German Test It is still another object of this invention to provide an Provisions for Class I-Explosives. explosive which is safer with respect to firedamp ignition. The following Table I gives some thermodynamic prop- Other and additional objects of this invention will beerties of various explosives for purposes of comparison.

TABLE I ExpL- Expl.- Smoke Specific Solids SaltMixture Heat Temp. Volume Energy Smoke (kcaL/kg.) K.) (l./kg.) (mt/kg.) Corngonents (Percent) 1 The specific energy is the product of the gas constant R, the smoke volume in mols pa kg. and the explosion temperature in K.

From Table I it can be noted that the specific energy of the salt combinations in accordance with the invention (III) is twice as high as the specific energy of (II). The

solid smoke components of (III) are, furthermore, twice as great as those of (I). It is thus shown that, for instance, the salt combination of the invention in accord-- ance with '(III) has a relatively high energy and at the same time a relatively large amount of solid smoke components.

Testing for ignition of firedamp is accomplished with a series of charge columns 50, 40, 30, 20 and 10 cm. in

length. The tested explosive has the following composition in Weight percents:

Nitroglycerine/nitroglycol (60/40 weight ratio) 29% Gun cotton 1% Ca(NO (50% aqueous solution) 3% Salt mixture Remainder It is another particular attribute of this invention that it avoids the use of ammonium nitrate. This is quite desirable because the exact grinding and the preparation of the ammonium nitrate are difiicult to achieve due to the ease with which it takes up moisture and its low transformation point (32 C.).

It is within the spirit and scope of this invention to utilize a ternary salt mixture having a particle size such that at least 30% and at most 95% pass through a screen of 0.1 mm. openings.

The explosives in accordance with the invention can also contain known combustible substances (for instance, parafiin, sawdust) or else halogen-containing combustible substances (for instance, chloroparafiins, waxes having a base of chlorinated naphthalene), Of course, in such case it must be seen to it that there is present an amount of oxygen-producing inorganic salts of salt mixtures (for instance, NaNO +NH C1 in a molar ratio of 1:1) which is sufficient for the combustion.

Furthermore, known inert materials (for instance, sodium chloride, iron oxide, etc.) can also be added to the explosives of the invention.

The advantages of the safety mining explosives of the invention reside in the fact that the deflagration safety with simultaneous increase in the energy is improved as compared with the previously known safety mining explosives of Class I.

The practice of this invention is illustrated by the following examples which are in no way to be construed as limiting.

EXAMPLES 1a-b Two explosives were prepared in known manner by mixing, the composition of the salts thereof being in accord with II and HI of Table I above. The two explosives withstood a methane/air mixture when tested in accordance with the German Provisions for Safety Mining Explosives of Class I (see Mining Ordinance concerning the distribution of explosives in mining of Ian. 28, 1959; cf. also article by Ahrens, Nobel-Heft of May 1959).

(la) Comparative example: Explosive in accordance with II of Table I above Explosive consisting of:

Nitroglycerin percent by wt 17.4 Nitroglycol do 11.6 Nitrocellulose do 1 50% calcium nitrate solution do 3 Ammonium nitrate do 26.5 Sodium chloride do 40 Sawdust do 0.5

Explosive properties:

Excess oxygen percent +5.5 Density g./cm. 1.6 Specific energy mt./kg 45.7 Detonation transfer lying free on sand cm 7 Deflagration safety: If a cartridge of the explosive is heated in a furnace to 100 C. and if it is seen to by the use of a kieselguhr envelope that an accumulation of heat can take place in the cartridge, then at the end of 2 hours there is an increase in temperature in the explosive to about 700 C. This temperature is retained for a few minutes. Since as is known a methane/ air mixture ignites at a temperature of 650 C. with an induction time of 10 seconds, firedamp igniting is to be expected if an explosive of this type which is under the influence for some time of a hot smoke of a neighboring shot, is thereby caused to defiagrate.

(lb) Explosive in accordance with the invention: Explosive in accordance with III 0 T able I abo ve Explosive consisting of:

Nitroglycerin percent by wt 17.4 Nitroglycol do 11.6 Nitrocellulose do 1 50% calcium nitrate solution do 3 Sodium nitrate do 27.5

Ammonium chloride do 28.8 Calcium carbonate ..do 10.7

Explosive properties:

Excess oxygen percent +0.85 Density g./cm. 1.58 Specific energy mt./kg 57.2

Deflagration safety: If a cartridge of this explosive is heated in a furnace to C. and if it is seen to by the use of a kieselguhr envelope that an accumulation of heat can take place in the cartridge, there takes place then in the explosive by the end of 21 hours only an increase in temperature of about 245 C. At this temperature, a methane/ air mixture will no longer be ignited.

A comparison of the above explosives shows that the composition in accordance with the invention has a 25% higher specific energy and favorable behavior with respect to heat. However, this behavior with respect to heat was definitely not to be expected in view of the large proportion of nitrates whose thermal decomposition can after all not be prevented by a substitution of the saltst What is claimed is:

1. In a plastic and gelatinous explosive composition comprising about 18 to 40 weight percent referred to the explosive of a gelatinous component formed of at least one liquid, possibly thickened nitric acid ester of a polyhydric alcohol and an inorganic salt component; the improvement which comprises utilizing as the inorganic salt component a ternary mixture consisting of ammonium chloride, alkali metal nitrate and alkaline earth metal carbonate.

2. The improved explosive claimed in claim 1, wherein said ammonium chloride bears a mole ratio to said alkali metal nitrate of about 1 to 2:1; said ammonium chloride bears a mole ratio to said alkaline earth metal carbonate of about 2 to 50:1; and said alkali metal nitrate bears a mole ratio to said alkaline earth metal'nitrate of about 3. The improved explosive claimed in claim 1, wherein said ammonium chloride bears a mole ratio to said alkali metal nitrate of about 1.2 to 1.7:1; said ammonium chloride bears a mole ratio to said alkaline'earth metal carbonate of about 5 to 25:1; and said alkali metal nitrate bears a mole ratio to said alkaline earth metal nitrate of about 3 to 15:1.

4. The improved explosive claimed in claim 1 containing, in addition to the named constituents, at least one oxygen liberating inorganic salt other than the aforementioned alkali metal nitrate and alkaline earth metal Detonation transfer lying free on sand cm carbonate and at least one other explosive combustible substance selected from the group consisting of paraflins, sawdust, chlorinated pa-rafi'lns and waxes having a base of chlorinated naphthalene.

5. The improved explosive claimed in claim 4 containing, in addition to the named constituents, at least one combustible chlorine-containing substance selected from the group consisting of chlorinated paraflins and waxes having a base of chlorinated naphthalene.

6. The improved explosive claimed in claim 1, wherein said inorganic salts have a particle size such that about 30 to 95 percent thereof will pass through a screen having 0.1 mm. openings.

7. The improved explosive claimed in claim 1, wherein said alkali metal is at least one selected from the group consisting of sodium, potassium and lithium.

8. The improved explosive claimed in claim 1, wherein said alkaline earth metal is at least one selected from the group consisting of calcium, magnesium, barium or mixtures thereof.

6 References Cited UNITED STATES PATENTS 2,829,036 4/1958 Berthmann et a1 149-62

Claims (1)

1. IN A PLASTIC AND GELATINOUS EXPLOSIVE COMPOSITION COMPRISING ABOUT 18 TO 40 WEIGHT PERCENT REFERRED TO THE EXPLOSIVE OF A GELATINOUS COMPONENT FORMED OF AT LEAST ONE LIQUID, POSSIBLY THICKENED NITRIC ACID ESTER OF A POLYHYDRIC ALCOHOL AND AN INORGANIC SALT COMPONENT; THE IMPROVEMENT WHICH COMPRISES UTILIZING AS THE INORGANIC SALT COMPONENT A TERNARY MIXTURE CONSISTING OF AMMONIUM CHLORIDE, ALKAKI METAL AND ALKALINE EARTH METAL CARBONATE.